Choosing the right Software development life cycle model

Selecting a Software Development Life Cycle (SDLC) methodology is a challenging task for many organizations. What tends to make it challenging is the fact that few organizations know what criteria to use in selecting a methodology to add value to the organization. Fewer still understand that a methodology might apply to more than one Lifecycle Model. Before considering a framework for selecting a given SDLC methodology, we need to define the different types and illustrate the advantages and disadvantages of those models (please see Software Development Life Cycle Models and Methodologies).

How to select the right SDLC

Selecting the right SDLC is a process in itself that organization can implement internally or consult for. There are some steps to get the right selection:

STEP 1: Learn the about SDLC Models

SDLCs are the same in their usage, advantages, and disadvantages. In order to select the right SDLC, one must have experience and be familiar with the SDLCs that will be chosen.

STEP 2: Assess the needs of Stakeholders

We must study the business domain, user requirements, business priorities, and technology constraints to be able to choose the right SDLC against their selection criteria.

STEP 3: Define the criteria

Some of the selection criteria or questions that you may use to select an SDLC are:

  • Is the SDLC appropriate for the size of our team and their skills?
  • Is the SDLC appropriate with the selected technology we use for implementing the solution?
  • Is the SDLC appropriate with client and stakeholders need and priorities
  • Is the SDLC appropriate for the geographical situation (co-located or geographically dispersed)?
  • Is the SDLC appropriate for the size and complexity of our software?
  • Is the SDLC appropriate for the type of projects we do?
  • Is the SDLC appropriate for our engineering capability?

What are the criteria?

Here is my recommended criteria, what will be yours?

Factors Waterfall V-Shaped Evolutionary Prototyping Spiral Iterative and Incremental Agile Methodologies
Unclear User Requirement Poor Poor Good Excellent Good Excellent
Unfamiliar Technology Poor Poor Excellent Excellent Good Poor
Complex System Good Good Excellent Excellent Good Poor
Reliable system Good Good Poor Excellent Good Good
Short Time Schedule Poor Poor Good Excellent Excellent Excellent
Strong Project Management Excellent Excellent Excellent Excellent Excellent Excellent
Cost limitation Poor Poor Poor Poor Excellent Excellent
Visibility of Stakeholders Good Good Excellent Excellent Good Excellent
Skills limitation Good Good Poor Poor Good Poor
Documentations Excellent Excellent Good Good Excellent Poor
Component reusability Excellent Excellent Poor Poor Excellent Poor

References

Selecting a Software Development Life Cycle (SDLC) Methodology.(2012, 3 18). Retrieved from http://www.smc-i.com/downloads/sdlc_methodology.pdf

Software Development Life Cycle Models. (2012, 3). Retrieved from Codebetter.com: http://codebetter.com/raymondlewallen/2005/07/13/software-development-life-cycle-models/

Software Development Life Cycle Models and Methodologies

Introduction

The software industry includes many different processes, for example, analysis, development, maintenance and publication of software. This industry also includes software services, such as training, documentation, and consulting.

Our focus here about software development life cycle (SDLC). So, due to that different types of projects have different requirements. Therefore, it may be required to choose the SDLC phases according to the specific needs of the project. These different requirements and needs give us various software development approaches to choose from during software implementation.

Types of Software developing life cycles (SDLC)

Waterfall Model

Description

The waterfall Model is a linear sequential flow. In which progress is seen as flowing steadily downwards (like a waterfall) through the phases of software implementation. This means that any phase in the development process begins only if the previous phase is complete. The waterfall approach does not define the process to go back to the previous phase to handle changes in requirement. The waterfall approach is the earliest approach that was used for software development.

WaterfallThe usage

Projects which not focus on changing the requirements, for example, projects initiated from request for proposals (RFPs)

Advantages and Disadvantages

Advantages Disadvantages
  • Easy to explain to the users.
  • Structures approach.
  • Stages and activities are well defined.
  • Helps to plan and schedule the project.
  • Verification at each stage ensures early detection of errors / misunderstanding.
  • Each phase has specific deliverables.
  • Assumes that the requirements of a system can be frozen.
  • Very difficult to go back to any stage after it finished.
  • A little flexibility and adjusting scope is difficult and expensive.
  • Costly and required more time, in addition to the detailed plan.

V-Shaped Model

Description

It is an extension of waterfall model, Instead of moving down in a linear way, the process steps are bent upwards after the coding phase, to form the typical V shape. The major difference between v-shaped model and waterfall model is the early test planning in the v-shaped model.

V-Shaped

The usage

  • Software requirements clearly defined and known
  • Software development technologies and tools is well-known

Advantages and Disadvantages

Advantages Disadvantages
  • Simple and easy to use
  • Each phase has specific deliverables.
  • Higher chance of success over the waterfall model due to the development of test plans early on during the life cycle.
  • Works well for where requirements are easily understood.
  • Verification and validation of the product in early stages of product development.
  • Very inflexible, like the waterfall model.
  • Little flexibility and adjusting scope is difficult and expensive.
  • Software is developed during the implementation phase, so no early prototypes of the software are produced.
  • The model doesn’t provide a clear path for problems found during testing phases.
  • Costly and required more time, in addition to detailed plan

Prototyping Model

Description

It refers to the activity of creating prototypes of software applications, for example, incomplete versions of the software program being developed. It is an activity that can occur in software development. It used to visualize some component of the software to limit the gap of misunderstanding the customer requirements by the development team. This also will reduce the iterations may occur in waterfall approach and hard to be implemented due to the inflexibility of the waterfall approach. So, when the final prototype is developed, the requirement is considered to be frozen.

It has some types, such as:

  • Throwaway prototyping: Prototypes that are eventually discarded rather than becoming a part of the finally delivered software

Throwaway prototyping

  • Evolutionary prototyping: prototypes that evolve into the final system through an iterative incorporation of user feedback.

ev-proto

  • Incremental prototyping: The final product is built as separate prototypes. At the end, the separate prototypes are merged in an overall design.

StagedModelofSDLC

  • Extreme prototyping: used at web applications mainly. Basically, it breaks down web development into three phases, each one based on the preceding one. The first phase is a static prototype that consists mainly of HTML pages. In the second phase, the screens are programmed and fully functional using a simulated services layer. In the third phase, the services are implemented

The usage

  • This process can be used with any software developing life cycle model. While this shall be focused with systems needs more user interactions. So, the system does not have user interactions, such as, a system does some calculations shall not have prototypes.

Advantages and Disadvantages

Advantages Disadvantages
  • Reduced time and costs, but this can be disadvantage if the developer loses time in developing the prototypes.
  • Improved and increased user involvement.
  • Insufficient analysis· User confusion of prototype and finished system.
  • Developer misunderstanding of user objectives.
  • Excessive development time of the prototype.
  • Expense of implementing prototyping

Spiral Method (SDM)

Description

It is combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts. This model of development combines the features of the prototyping model and the waterfall model. The spiral model is favored for large, expensive, and complicated projects. This model uses many of the same phases as the waterfall model, in essentially the same order, separated by planning, risk assessment, and the building of prototypes and simulations.

spiral

The usage

It is used in shrink-wrap large applications and systems which built-in small phases or segments.

Advantages and Disadvantages

Advantages Disadvantages
  • Estimates (i.e. budget, schedule, etc.) become more realistic as work progressed, because important issues are discovered earlier.
  • Early involvement of developers.
  • Manages risks and develops the system into phases.
  • High cost and time to reach the final product.
  • Needs special skills to evaluate the risks and assumptions.
  • Highly customized limiting re-usability

Iterative and Incremental Method

Description

It is developed to overcome the weaknesses of the waterfall model. It starts with an initial planning and ends with deployment with the cyclic interactions in between. The basic idea behind this method is to develop a system through repeated cycles (iterative) and in smaller portions at a time (incremental), allowing software developers to take advantage of what was learned during the development of earlier parts or versions of the system.

It consists of mini waterfalls

incremental-sdlc

The usage

It is used in shrink-wrap application and large system which built-in small phases or segments. Also can be used in a system has separated components, for example, ERP system. Which we can start with the budget module as a first iteration and then we can start with inventory module and so forth.

Advantages and Disadvantages

Advantages Disadvantages
  • Produces business value early in the development life cycle.
  • Better use of scarce resources through proper increment definition.
  • Can accommodate some change requests between increments.
  • More focused on customer value than the linear approaches.
  • Problems can be detected earlier.
  • Requires heavy documentation.
  • Follows a defined set of processes.
  • Defines increments based on function and feature dependencies.
  • Requires more customer involvement than the linear approaches.
  • Partitioning the functions and features might be problematic.
  • Integration between iteration can be an issue if this is not considered during the development.

Extreme programming (Agile development)

Description

It is based on iterative and incremental development, where requirements and solutions evolve through collaboration between cross-functional teams.

SW-FW-design

The usage

It can be used with any type of the project, but it needs more involvement from the customer and to be interactive. Also, it can be used when the customer needs to have some functional requirement ready in less than three weeks.

Advantages and Disadvantages

Advantages Disadvantages
  • Decrease the time required to avail some system features.
  • Face to face communication and continuous inputs from customer representative leaves no space for guesswork.
  • The end result is the high-quality software in the least possible time duration and satisfied customer.
  • Scalability.
  • The ability of the customer to express user needs.
  • Documentation is done at later stages.
  • Reduce the usability of components.
  • Needs special skills for the team.

References

(2012, March). Retrieved from Wikipedia: http://en.wikipedia.org/wiki/Main_Page

(2012, March). Retrieved from Software Developing life cycles: http://www.sdlc.ws

Software Development Life Cycle Models. (2012, 3). Retrieved from Codebetter.com: http://codebetter.com/raymondlewallen/2005/07/13/software-development-life-cycle-models/